Designed to be installed on any add on furnace. Specifically, it covers the blowers and allows for connection to the existing HVAC return duct work or to newly installed ducting. It comes with an integrated slot for a 16" x 20" air filter. Made of durable Galvanized steel. For units: 1300, 1537G, 1602, 1802, 24AF, 1400, 1500, 1557M, 1602M, 24A, and 30A.